With the firewall configured, it was time to set up Fail2ban. It can be installed from pkg, along with pyinotify for kqueue support.

~~~
pkg install py37-fail2ban-0.11.1_2
pkg install py37-pyinotify-0.9.6
~~~

The default configuration is in /usr/local/etc/fail2ban/jail.conf, and overrides should be put in jail.local. First I needed to tell Fail2ban to use PF.

~~~
[DEFAULT]
banaction = pf
~~~

his refers to the file /usr/local/etc/fail2ban/action.d/pf.conf, which adds banned IP addresses to a PF table called fail2ban. This on its own doesn’t do anything but register the address with PF, so I needed to add a rule to pf.conf to block the traffic.

~~~
table <fail2ban> persist
block in quick from <fail2ban>
~~~

I added this rule directly below block in all so that it took precedence over my ICMP rules.

Back to Fail2ban, I enabled the SSH jail, which watches for failed logins in /var/log/auth.log.

~~~
[sshd]
enabled = true
~~~

Then I reloaded the PF configuration and started Fail2ban.

~~~
service pf reload
echo 'fail2ban_enable="YES"' >> /etc/rc.conf
service fail2ban start
~~~

To see it in action, I can tail the Fail2ban log, list the addresses in the fail2ban table, and inspect the statistics for my PF rules.

~~~
tail /var/log/fail2ban.log
pfctl -t fail2ban -T show
pfctl -v -s rules
~~~

My final jail.local looks like this:

~~~
[DEFAULT]
bantime = 86400
findtime = 3600
maxretry = 3
banaction = pf

[sshd]
enabled = true
~~~


https://www.sqlpac.com/fr/documents/linux-ubuntu-fail2ban-installation-configuration-iptables.html
https://cmcenroe.me/2016/06/04/freebsd-pf-fail2ban.html